The manual may have the option of selecting a fixed lower thrust setting for take-off.
In the 747-400 (RR engines) you can select fixed thrust derates (TO-1 or TO-2) which will yield a lower Vmcg. I think that these can then be further reduced using the 'assumed temp' method. (Not exactly sure, as I've never had to use TO-1 or TO-2.) A comparison of Vmcg for Sea Level, OAT +15C gives 123, 117, 111 for full TO, TO-1 and TO-2, respectively.
There is a warning when using the 'fixed' derates to the effect that in the event of engine failure, advancing the thrust levers could result in a loss of directional control.
My understanding of 'overspeed' is that if you are climb limited (but not runway limited) you can get a better second segment gradient by using a higher V2. You also have to increase the V1 and Vr but as you have 'extra' runway, that should not be a problem. I think JT is suggesting that this technique would help by increasing the V1 to a higher value than the Vmcg.
Not trying to put words in your mouth JT, just giving my interpretation!